I guess your wireless driver hasn’t been installed. That problem is pretty simple. The hard part is you can’t install driver without internet (Actually you can do it with your phone and USB tethering mode)

If you run lspci command, you will see your hardware information, include wireless adapter type. You can search for driver package name with it. Read “Debian install wireless driver” on google can help you so much. If you have any question please ask me here, i will help you as much as possible